A gene mutation known to make flu viruses resistant to Roche Holding AG (ROG)’s Tamiflu was identified in two patients infected with the H7N9 bird flu virus in China, a study found. The gene was discovered in two of three patients who became the most severely ill in a study of 14 patients treated with Tamiflu after being admitted to a Shanghai hospital in April with H7N9 infection, according to an article published in The Lancet medical journal today. In one patient, the resistance developed after the initial infection, suggesting treatment with Tamiflu may have spurred the mutation. The finding is the first official confirmation of resistance to Tamiflu. In the other patients, treatment with the drug was associated with clearing the virus, and early treatment of suspected or confirmed cases is “strongly encouraged,” wrote a group of researchers led by Zhenghong Yuan of Fudan University.